VentureStar was a single-stage-to-orbit (SSTO) reusable launch system proposed by Lockheed Martin and funded by the U.S. government. The goal was to replace the Space Shuttle by developing a re-usable spaceplane that could launch satellites into orbit at a fraction of the cost. Design specifications called for the use of linear aerospike engines that maintain thrust efficiency at all altitudes. VentureStar was essentially a bigger version of the X-33 but was not produced after failures with the X-33 subscale technology demonstrator test vehicle, funding was cancelled in 2001.


aerospike engine By NASA Marshall Space Flight Center (NASA-MSFC) [1], Papa Lima Whiskey (restoration credit) - http://nix.ksc.nasa.gov/info;jsession..., CC BY-SA 3.0, https://commons.wikimedia.org/w/index...